Inuyasha Spoiler:

Ryuukotsusei

Ryuukotsusei is the dragon that killed Inu Yasha's father, but was sealed away in the process. When Inu Yasha says Tessuaiga has become too heavy, he has to make it lighter by taking out Ryuukotsusei's heart. Naraku wakes up Ryuukotsusei and Inu Yasha defeats him using the Bakuryuuha, Tessuiga's ultimate attack (real cool).
Submitted by RandomL